ما حكم من سب دين النصارى؟

If the intent behind reviling the Christian religion is the religion brought by Jesus, peace be upon him, then reviling it is impermissible and considered disbelief (kufr), because Muslims believe in all prophets and make no distinction between any of His messengers. However, if the intent is what the Christians innovated in terms of distortion, alteration, and polytheism (shirk), then there is no objection to reviling it and describing its adherents as polytheists and disbelievers. But this is not permissible if it leads to reviling Islam or its Prophet, as a preventive measure (sadd al-dhari'a).